Grid structure for color picture tubes

ABSTRACT

A support for the grid structure of a cathode-ray tube in which the support is stressed to compensate for any expansion of the grid wires due to heating, the support having a pair of opposed parallel arms with the grid wires attached to and extending transversely between the arms, and a pair of braces supporting the arms at the Bessel points, the braces being stressed in a direction substantially parallel to the direction of the grid wires so that as the grid wires expand due to heat the braces will expand a corresponding amount to maintain a substantially constant tension of the grid wires.

O United States Patent 1151 3,638,063 Tachikawa et al. 5] Jan. 25, 1972[54] GRID STRUCTURE FOR COLOR 2,701,847 2/1955 Yanagisawa et al...313/269 x I U E UBE I 3,436,585 4/1969 Murakami ..3l3/348 C R T S3,487,253 12/1969 Scharmann ..313/269 [72] Inventors: Takuji Tachikawa;Akio Ohgoshi; Joshida 2,832,911 4/1958 Van Velzer ..313/78 Susumu; AklraNakayama; Eiji lshii, all of Tokyo, Japan 1 Primary ExaminerDavidSchonberg I Assistant ExaminerToby H. Kusmer [73] Asslgnee' SonyCorporation Tokyo Japan Attorney Albert C. Johnston, Robert E. lsner,Lewis H. [22] Filed: Jan. 10, 1969 Eslinger and Alvin Sinderbrand 0 Asupport forthe grid structure of a cathode-ray tube in which [30]Forelgh pp ation Priority D v the support is stressed to compensate forany expansion of the Jan. 1 1, 1968 Japan ..43/1658 grid Wires due toheating, the pp having a P of pp Jan. 11, 1968 Japan ..43/165 P r armswith the grid Wires attached to and extending transversely between thearms, and a pair of braces supporting 52 0.5.0 ..3l3/348, 313/269 thearms at the Bessel Points, the braces being Stressed in a 5 [nLCL I IHolj 4 direction substantially parallel to the direction of the grid[58] Field of Search ..313/269, 348, 78 Wires so that as the grid wiresexpand due to heat the braces will expand a corresponding amount tomaintain a substan- 5 References Cited tially' constant tension of thegrid wires.

UNITED S T PATENTS 9 Claims, 13 Drawing Figures 2,446,271 8/1948 Eitel..3 13/348 X PATENTEDJAHZSIHTZ 3.638.063

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BY ATTORNEYS PATENTEB M25 i972 SHEET 8 BF 7 TAN/J1 TACHIKAWA AKIOOHGOSHI Sl/Sl/MU YOSHIDA AKIRA NAKAXAMA INVENTOR. EIJI ISHH ATTORNEYSGRID STRUCTURE FOR COLOR PICTURE TUBES This invention relates to a novelgrid structure for color picture tubes, and more particularly to a gridstructure which is of particular utility when employed in color picturetubes.

As is well known in the prior art, color cathode ray tubes employ, forelectron beam postdeflection and focusing, a grid structure such that aplurality of parallel grid wires are stretched across a parallelogramicframe between a pair of opposed sides. Such a grid structure is producedin the following manner. A plurality of parallel grid wires arestretched on a master frame under predetermined'taut conditions and agrid frame is put on the grid wires from inside of the master frame. Thegrid wires are then fixed to a pair of opposed supports of the gridframe and are thereafter severed along the margins of the grid frame. Inthis case, the grid frame is prestressed inwardly by a turnbuckle toapply a maximum tension to the grid wires secured to the central portionof the opposed supports of the grid frame and a smaller tension to thosefixed to end portions of the supports, ensuring that all the grid wiresare subjected to substantially uniform tension by the restoring force ofthe prestressed grid frame after disassembling it from the master frame.

Such a grid structure may be regarded as one where a plurality of gridwires are stretched at substantially uniform tension on aparallelogramic frame prestressed in a manner to be displaced the mostat the center of the frame. When a predetermined positive potential isapplied to such a grid structure and electron beams are emitted from theelectron gun of a cathode ray tube toward the fluorescent screenthereof, electron beams of several to lO-odd percent strike against thegrid wires and are discharged therethrough to thereby heat the gridwires. As a result of this, the temperature of the grid wires is raisedseveral-l degrees and the wires expand. An examination of the expandedgrid wires shows that since the displacement of the frame is greatest atthe center thereof, elongation of the grid wires of that portion due tothermal expansion is cancelled by the restoring force of the prestressedframe as if the grid wires had not been elongated. Accordingly, the gridwires are still subjected to substantially the same original tension,and hence do not sag. The elongation of the grid wires lying on bothsides of the central grid wires cannot be absorbed with the displacementof the frame at those particular portions, since the displacement isbasically small. Consequently, when the elongation of the grid wiresexceeds the displacement of the frame, the grid wires are likely to sag.Even if the grid wires do not sag, they are not pulled at apredetermined tension and are readily vibrated at great amplitude tolower the picture quality of the reproduced picture when subjected toaccidental small shocks.

The above can easily be understood from the fact that when all the gridwires have substantially the same length 1, their elongation resultingfrom thermal expansion is l and the amount of restoration of thedistorted frame is l at the center thereof, the amount of restoration ofthe frame on both sides of the center thereof is smaller than that atthe central portion.

This defect is remarkable especially in the grid structure of a colorcathode ray tube of the type where a plurality of ribbonlike gridelements are stretched in parallel with phosphor strips and function asa kind of shadow mask. In this type of structure three electron beamsare impinged upon three different color emissive phosphor strips throughslits defined between adjacent grid elements.

A grid structure such as described above has been proposed in an attemptto increase the electron beam transmission factor of the so-calledshadow mask in which a plate having bored therethrough a plurality ofapertures is used as a mask for the electron beam. In such a gridstructure, however, the grid elements are secured only at both ends tothe frame, so that the grid elements heated by electron beams strikingthereon radiate heat mainly through the ends fixed to the frame.

Further, the transmission factor of the electron beam through such agrid is lO-odd to 20-odd percent and the temperature of the gridelements rises up to 100 to 130 C. Consequently remains unchanged. As aresult of this, there is the possibility that the electron beam strikeson a phosphor strip other than a predetermined one, especially aphosphor strip adjacent the predetermined one to cause unnecessary coloremission. Therefore, the nonuniformity in the tension applied to thegrid elements should be avoided.

. Accordingly, one object of this invention is to provide a gridstructure which is adapted such that the grid elements are alwayssubjected to a predetermined tension and do not sag dur- .ing operation,though heated by electron beams.

Another object of this invention is to provide a grid structure forshadow-mask type color cathode ray tubes in which the grid elementsheated by electron beams do no sag during operation to thereby ensureuniformity in the spacing between adjacent grid elements and henceprevent unnecessary bombardment of the phosphor strips by the electronbeam.

Still another object of this invention is to provide a grid structurewhich is constructed such that the grid elements are protected fromshocks applied from the outside and caused by electron beam bombardment.

Other objects, features and advantages of this invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 and 2 are schematic diagrams for explaining the presentinvention;

FIG. 3 is a plan view showing one example of a grid structure for colorcathode ray tubes produced according to this invention;

FIG. 4 is a side view of the grid structure illustrated in FIG.

FIG. 5 is a plan view illustrating another example of the grid structureof this invention;

FIG. 6 is a schematic diagram showing the manner in the grid elementsare mounted on a grid frame;

FIG. 7 is a plan view showing another modified form of the presentinvention;

FIG. 8 is a cross-sectional view taken along the line A-A in FIG. 7;

FIG. 9 illustrates in perspective the plate supports employed in theexample of FIG. 7;

FIG. 10 similarly shows in perspective a resilient support;

FIG. 11 is a plan view showing still another modification of the presentinvention;

FIG. 12 is a side view of the grid structure depicted in FIG. 1 l; and

FIG. 13 is a perspective view of the grid structure shown in FIG. 11. l

FIG. 1 is a schematic diagram showing displacement (indicated by brokenlines) of a bar 1 of a length having two fulcra 2A and 28 when subjectedto a uniformly distributed load 3 acting substantially perpendicular tothe bar. In order to minimize the displacement of the bar 1, the fulcra2A and 2B are located at such positions that the displacement 6 1 ofboth end portions of the bar 1 is equal to the displacement 8 of thecentral portion. Such positions of the fulcra are referred to as theBessel points, and when the distance from the end of the bar 1 to thefulcrum 2A or 2B is taken as b, b/L=0.223. The length L of the bar doesnot indicate the actual length but a rang over which the load 3 isapplied.

If a pair of such bars are arranged in parallel relation as a pair ofopposed frame members of a grid frame, a plurality of grid wires orelements stretched between the frame members which at substantiallyuniform tension are subjected to the aforementioned uniformlydistributed load 3. In other words, where a pair of bars 1 and 1 (notshown) ofa length L constituting two frame members are arranged inparallel relation and a plurality of parallel grid wires or elements arestretched between the bars substantially at right angles thereto underapproximately uniformly tensioned conditions and fulcra 2A, 2B and 2A'28 (not shown) respectively supporting the bars are located atpositions satisfying the aforementioned requirement b/L=0.223, the barsare deformed to be bent at both ends and between the fulcra by the loadcaused by the tension of the grid wires or elements in a direction ofthe tension but the displacement ration, that is, the displacement perunit load is at minimum. Consequently, the displacement ratio of theframe of this invention (indicated by the broken line B in FIG. 2) isfar smaller than that of the conventional grid frame (indicated by thefull line A in FIG. 2) of the type where the fulcra are located at bothends of two bars constituting the frame members, and accordingly thegrid frame of this invention virtually deformed as compared with thedeformation of the conventional grid frame. If the rigidity of the bar 1is increased up to maximum, the deformation ofthe frame can beneglected.

The tension of the rid wires or elements stretched between the two barsI and 1 (not shown) corresponding to the load 3 shown in FIG. 1 isproduced by pressing the two bars with a resilient support (not shown)in a direction opposite to the load 3 in a manner to force away the twofulcra 2A and 2A (2A not shown) and 2B and 28' not shown) from eachother. Referring now to FIGS. 3 to 10, the construction of the gridstructure of this invention will be described in detail by way ofexample.

As clearly shown in the figures, the grid structure of this inventioncomprises a frame of a predetermined configuration which consists of barsupports 4 and 4' corresponding to the aforementioned bars I and l and apair of substantially C- shaped resilient supports 5 and 5 supportingthe bar supports 4 and 4 at or in the vicinity of the Bessel points B Band B B thereof, and a plurality of ribbon-shaped grid elements of, forexample, stainless steel are stretched between the bar supports 4 and 4'at a predetennined pitch under predetermined distribution of tension.Reference numeral 7 indicates generally the grid structure.

The bar supports 4 and 4' may be formed ofa metal such as iron,stainless steel or the like and in the illustrated example the barsupports 4 and 4' are square in cross section and are bent to conform tothe panel to which the grid structure will be attached. The resilientsupports 5 and 5' may be formed of a metal such as iron, stainless steelor the like and are substantially C-shaped so as not to disturb theirradiation of the phosphor screen by the electron beam emitted from theelectron gun ofa cathode ray tube. It is a matter of course that thesupports 5 and 5' may be configured at will so long as they do notdisturb the electron beam directed to the fluorescent screen of thecathode ray tube. The grid elements 6 may also be formed ofa metal suchas iron, stainless steel or the like.

With such an arrangement, since the pair of bar supports 4 and 4constituting one portion of the frame are jointed to the resilientsupports 5 and 5 as a unitary structure at or in the vicinity of theBessel joints BA, B and B and B8. The bar supports 4 and 4' may beregarded as a rigid body with respect to the load caused by the tensionof the grid elements. Accordingly, when the grid elements 6 that arestretched between the bar supports 4 and 4' uniformly at a predeterminedtension expand by heat resulting from the electron beam bombardmentthereon, the bar supports 4 and 4 are pulled outwards by the resilientsupports 5 and 5' in a parallel relationship by a distance correspondingto the length ofthe grid elements which have been extended by thethermal expansion. Consequently, although the absolute value of thetension is different from the initial one, the initial distribution ofthe tension over the entire grid elements remains unchanged.

The foregoing description has been made in connection with a gridstructure in which the grid elements are of substanlength of the gridelements on the end portions of the bar supparts were. l75 mm and IIEIQfIhF elements of the central portion: 185 mm.) were stretched betweenthe bar supports at a tension of about 350 g. for each grid element, ithas been ascertained that although the grid elements were heated byelectron beams and extended due to thermal expansion during operation,accidents such as vibration of the grid elements due to nonuniformity ofthe tension or color contamination due to irregularity of the spacebetween adjacent grid elements were not caused. Further, it has beenfound that the deviation from the initial distribution of the tension ofthe grid elements caused by the thermal expansion thereof resulting fromthe collision of the electron beam therewith were compensated for by thestretch or shrinkage of the grid elements or slight restoring force ofthe bar supports.

In addition, it has also been found that if the deviation of the lengthof the grid elements is in a range of :20 percent relative to its meanvalue, the length of the grid elements extended by the thermal expansionis extremely short and the initial distribution of the tension of thegrid elements is maintained during operation by the stretch andshrinkage of the grid elements or by compensation due to the restoringforce of the bar supports.

In the prior art a very complicated device is required for stretchinggrid elements on a grind frame, but this can be readily achieved by thefollowing method. As shown in FIG. 5, for example, a thin stainlesssteel plate 8 of a predetermined size is first prepared and is subjectedto etching to remove selected areas, thus providing metal strips 8aarranged at a predetermined pitch. At the same time, slits 8b are formedfor a predetermined number of metal strips 8a (every three metal stripsin the figure) in the plate 8 at both marginal portions thereof. In asimilar manner, slits 8c are formed in the plate 8 on both sides of themetal strips 8a. Portions 8d separated by the slits 8b are thenrespectively held by chucks 9A and 9B as shown in FIG. 6. In this case,the number of the chucks 9A and 98 corresponds to that of the portions8d. The chucks 9B are supplied with a moderate tension in accordancewith the thickness and the quality of material of the portions 8d, butsuch tension may be applied to both of the chucks 9A and 9BSubstantially the same tension is applied to the metal strips by meansof, for example, a coiled spring 10 as shown in the figure. Under suchtaut conditions, a pair of bar supports 11 and 11' are disposed underthe plate 8 at predetermined positions and the plate 8 is welded to thebar supports. In this case, the bar supports 11 and 11 are supported bya pair of resilient supports at or in the vicinity of their Besselpoints, though not shown, and the resilient supports are slightly bentinwardly so as to apply a predetermined tension to the metal strips whenthe portions 8d are released from the chucks 9A and 9B. It is preferredthat the force for bending the two resilient supports be equal to thetension (the total tension of all the metal strips) applied to the metalstrips by the spring 10. In such a case when the chucks 9A and 9B areremoved, the tension of the metal strips 8a due to the spring 10 isapplied to the strips 8a by the resilient supports, so that the tensionof the metal strips 8a remains unchanged before and after the removal ofthe chucks.

Subsequent to the welding of the plate 8, the portions 8d projectingoutside of the bar supports 11 and 11' are cut off and both end portionsof the slits 8c are also cut off. The slits 8c are provided forfacilitating the cutting of the plate 8, and hence they are not alwaysnecessary. In the manner described above, the metal strips 8a canreadily be stretched between the bar supports 11 and 11 withpredetermined distribution of the tension. In this use, the metal strips8a are coupled together at both ends. It is possible, of course, thatthe end portions of the metal strips 8b are provided for preventing theplate 8 from becoming creased when applying a tension to the edges ofthe plate 8 and for ensuring uniformity of the tension applied to eachmetal strip 80. In the absence of the slits 8b, it is extremelydifficult to apply the tension to the metal strips 8a with thepredetermined distribution.

While the metal strips 8a are subjected to substantially equal tensionby the chucks 9A and 9B in the above example, the distribution of thetension may be changed as desired in accordance with the shapes of thebar supports and the resilient supports and the condition of theresilient supports welded to the bar supports in the vicinity of theBessel points thereof to ensure uniformity of the tension applied to themetal strips by the resilient supports.

The electron beam transmission factor depends upon the width of themetal strips or the diameter and the pitch of the metal wires, which areusually selected to render the electron beam transmission factorapproximately 20 percent in view of the relationship to the width ofeach phosphor strip of the fluorescent screen of cathode ray tubes.

In FIGS. 7 and 8 there is illustrated another example of this invention,in which reference numeral designates generally a grid structure. A pairof plate supports 12 and 12' are supported by a frame like resilientsupport 13 at or in the vicinity of their Bessel points to provide aframe of a predetermined configuration, and grid elements 14 in the formof, for example, metal strips are stretched between the pair ofplatelike supports 12 and 12'.

The plate supports 12 and 12' may be formed of a metal such as iron,stainless steel or the like and, as shown in FIG. 9, one marginal edgeof each plate support is curved so as to conform to the surface of thepanel of a cathode ray tube with which the finished grid structure willbe assembled. The resilient support 13 may also be formed of a metalsuch as iron, stainless steel or the like and this support 13 hasprojections 13a at places substantially corresponding to the Besselpoints of the plate supports 12 and 12 as illustrated in FIG. 10.Further, the support 13 has L-shaped plate support-retaining members 13bformed integrally at places corresponding to the projections 13a.

The pair of plate supports 12 and 12' are mounted on the retainingmembers 13b of the resilient support 13 in such a manner that theprojections 13a of the support 13 engage the plate supports 12 and 12 ator in the vicinity of their Bessel points, and the plate supports andthe resilient supports are held together by predetermined jigs in amanner to produce a predetermined pressure at or in the vicinity of theBessel points of the plate supports 12 and 12 by the projections 13a ofthe resilient support 13. Then, the grid elements 14 are stretchedbetween the pair of plate supports 12 and 12 at a predetermineddistribution of tension.

With such an arrangement, the pair of plate supports 12 and 7 12' aresupported by the projections 13a of the resilient support 13 at or inthe vicinity of their Bessel points, so that the equilibrium of thetension is very stable after the grid elements 14 have once beenstretched at the predetermined distribution of the tension. Accordingly,the equilibrium of the tension is not lost by a slight variation in thetension after stretching the grid elements 14 and the grid frame is notdeformed. Further, the equilibrium of the tension is difficult to looseby thermal expansion of the frame or the grid elements 14 due to atemperature rise during operation, and even if the equilibrium of thetension is lost, the tension promptly balances, so that deformation ofthe frame is very slight. Consequently, the position of the gridelements 14 is not shifted and the electron beam always impinges uponthe fluorescent screen accurately at a predetermined location, so thatphenomenon such as color contamination is not caused thereby ensuringreproduction of a clear picture. In addition, since the grid structuredescribed above is simple in construction, its fabrication is easy andthe yield is greatly increased. Even if the grid elements 14 arestretched between the plate supports 12 and 12' at substantially uniformtension, the deformation of the frame is very slight as indicated by thedotted line B in FIG. 2. Accordingly, there is no possibility that theposition of the grid elements 14 is shifted by a slight deformation ofthe frame and by thermal expansion of the grid elements or the frame dueto a temperature rise. That is, even if the grid elements 14 arestretched at uniform tension, the aforementioned many advantages canstill be obtained.

The assembling of the grid structure with the panel of a cathode raytube can readily be achieved by the same means as mentioned previouslyor by other known means, and accordingly no description will be given.Further, it is needless to say that the aforementioned method can beused for stretching the grid elements, and the metal wires may bestretched at the grid elements 14 at a predetermined pitch in place ofthe metal strips.

The foregoing description has been made in connection with only severalexamples of this invention, and the material, shape and the like of thebar supports, plate supports, grid elements, resilient supports and soon can be suitably selected at will, if necessary. However, the barsupports and the plate supports are desired to be formed of a conductivematerial so as to establish electric fields between the supports and thegrid elements. Further, these supports are not restricted to the bar andplate supports.

When the grid structure is used in color picture tubes the grid elementsare caused to vibrate by mechanical vibration due to external shocks orelectron beam bombardment. In FIGS. 11 to 13 there is shown stillanother example of this invention in which the grid structure isdesigned to prevent such unwanted vibration of the grid elements.

In the figures reference numerals 21A 22B represent substantiallyC-shaped resilient supports supporting the bar supports 21A and 21B ator in the vicinity of their Bessel points to constitute a grid framegenerally designated by 23. Reference numeral 24 identified gridelements such as ribbonlike metal strips which are stretched between thepair of bar supports 21A and 218 at a predetermined tension distributionand pitch. These members are identical with those described in theforegoing examples.

In the present example, a damping rod formed of, for example, a metalwire is provided in contact with the grid elements 24.

For example, resilient pieces 26A and 26B are planted on the outside ofthe resilient supports 22A and 22B substantially at the center thereof,and the damping rod 25 is stretched between the resilient pieces 26A and268. In this case the damping rod 25 is stretched in a direction of thelines of the raster (in the electron beam-scanning direction) and it ispreferred that the damping rod 25 be stretched obliquely in a range of30 to 45 relative to the electron beam scanning direction.

With such an arrangement, the grid elements 24 are resiliently pressedby the damping rod 25, and hence are not likely to be caused to vibrateby mechanical shocks from the outside and electron beam bombardment.Even if vibration occurs, it is immediately suppressed by the dampingrod 25, thus preventing a bad influence by the vibration of the gridelements. The provision of the damping rod 25 avoids not only thevibration of the grid elements but also irregularity in the spacingthereof which results from twisting of the grid elements. Namely, whenthe grid elements 24 are heated by collision of the electron beamtherewith and are to be twisted due to thermal expansion, the dampingrod 25 presses the grid elements 24 to prevent twisting of the gridelements to hold the space between adjacent grid elements aspredetermined, ensuring that the electron beam impinges only on apredetermined phosphor strip. Further, the provision of the damping rod25 is only to stretch it in contact with the surfaces of the gridelements and hence can be achieved with great ease. The damping rod 25may be a mechanically strong metal wire of, for example, tungsten,stainless steel, inconel or the like. The use of such a mechanicallystrong wire avoids breakage of the damping rod or insufficient pressingof the grid elements as with conventional damping rods of glass fiber ingrid structures for the Chromatron (Registered Trademark) type picturetubes.

The damping rod 25 formed of the above-mentioned metals or other ones ispreferred in terms of mechanical strength and is free from secondaryelectron beam emission by the electron beam. It is preferred that thediameter of the damping rod 25 to 30 to 50 microns. With a diameter of,for example, 100 microns, the mechanical strength of the damping rodincreased but the reproduced picture is adversely affected by thedamping rod. With a diameter of less than 30 microns, the mechanicalstrength of the rod 25 decreases and its pressing effect of the gridelements becomes weak. With a smaller diameter damping rod, the badinfluence on the reproduced picture is decreased correspondingly, butthe influence of a damping rod 50 microns in diameter on the reproducedpicture is hardly noticeable. According to our experiments, a tungstenwire of a diameter from 30 to 50 microns yields good results. In theforegoing example, the damping rod 25 is stretched between the tworesilient pieces 26A and 268 but either or both of them may be dispensedwith. The shape and position of the resilient pieces are not limited tothose in the above example. For example, it is possible that resilientwires are stretched on the frame on both sides of the grid elementsinstead of the resilient pieced and the damping rod is stretched betweenthe resilient wires. Further, the damping rod 25 may be attached to thegrid elements 25.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thisinvention.

What is claimed is:

l. A support for the grid elements of a cathode ray tube comprising apair of opposed parallel arms, a plurality of said grid elements affixedto said arms and extending transversely therebetween, a pair ofgenerally C-shaped braces supporting said arms and attached theretosubstantially at the Bessel points and formed to lie in surfacessubstantially parallel to the surface defined by said grid elements,said braces being stressed a sufficient amount in a directionsubstantially parallel to the direction of said grid elements whereby assaid grid elements expand said braces expand a corresponding amount tomaintain the tension on all of said grid elements substantially uniform.

2. A support for a grid structure of a cathode ray tube comprising apair of opposed parallel arms, a plurality of flexible grid wiresaffixed to said arms and extending therebetween, a pair of mechanicallyresilient braces supporting said arms and attached thereto at locationsinwardly spaced from the ends of said arms substantially at the Besselpoints, and said braces being stressed in a direction substantiallyparallel to the direction of said flexible grid wires to apply tensionstress to said grid wires whereby as said flexible grid wires expand dueto heat generated during the operation of the tube, said braces expanddue to their resiliency and their being stressed a corresponding amountto maintain the tension on all of said flexible grid wires substantiallyuniform.

3. A support in accordance with claim 2 wherein said braces aresubstantially C-shaped.

4. A support in accordance with claim 2 wherein a damping rod extendsover said flexible members to substantially eliminate mechanicalvibration of said flexible members.

5. A support in accordance with claim 4 wherein said damping rod isstretched between said braces.

6. A support in accordance with claim 5 wherein said damping rod isflexible and is attached substantially to the center of said braces.

7. A support according to claim 6 wherein the damping rod is inclinedrelative to flexible grid wires.

8. A support in accordance with claim 6 wherein said damping rodresiliently presses against said flexible members.

9. A support according to claim 8 wherein said damping rod has adiameter of between 30 and 50 microns.

1. A support for the grid elements of a cathode ray tube comprising apair of opposed parallel arms, a plurality of said grid elements affixedto said arms and extending transversely therebetween, a pair ofgenerally C-shaped braces supporting said arms and attached theretosubstantially at the Bessel points and formed to lie in surfacessubstantially parallel to the surface defined by said grid elements,said braces being stressed a sufficient amount in a directionsubstantially parallel to the direction of said grid elements whereby assaid grid elements expand said braces expand a corresponding amount tomaintain the tension on all of said grid elements substantially uniform.2. A support for a grid structure of a cathode ray tube comprising apair of opposed parallel arms, a plurality of flexible grid wiresaffixed to said arms and extending therebetween, a pair of mechanicallyresilient braces supporting said arms and attached thereto at locationsinwardly spaced from the ends of said arms substantially at the Besselpoints, and said braces being stressed in a direction substantiallyparallel to the direction of said flexible grid wires to apply tensionstress to said grid wires whereby as said flexible grid wires expand dueto heat generated during the operation of the tube, said braces expanddue to their resiliency and their being stressed a corresponding amountto maintain the tension on all of said flexible grid wires substantiallyuniform.
 3. A support in accordance with claim 2 wherein said braces aresubstantially C-shaped.
 4. A support in accordance with claim 2 whereina damping rod extends over said flexible members to substantiallyeliminate mechanical vibration of said flexible members.
 5. A support inaccordance with claim 4 wherein said damping rod is stretched betweensaid braces.
 6. A support in accordance with claim 5 wherein saiddamping rod is flexible and is attached substantially to the center ofsaid braces.
 7. A support according to claim 6 wherein the damping rodis inclined relative to flexible grid wires.
 8. A support in accordancewith claim 6 wherein said damping rod resiliently presses against saidflexible members.
 9. A support according to claim 8 wherein said dampingrod has a diameter of between 30 and 50 microns.